As a light source for backlight of a liquid crystal display device, e.g., a discharge lamp such as cathode ray tube is widely used. In general, this discharge lamp is lit-on with AC by a discharge lamp lighting device having an inverter. In recent years, corresponding to high luminance and large scale of the liquid crystal display device, as an illumination light source of this liquid crystal display device, a multiple-light backlight using a plurality of discharge lamps is frequently used.
Since the light-on operation of the discharge lamp generally requires a high voltage, the discharge lamp lighting device normally has an inverter transformer that generates a high voltage on the secondary side, inverter means that generates a high-frequency voltage is connected to the primary side of the inverter transformer and a discharge lamp and a so-called Ballast element for stabilizing tube current of the discharge lamp having a negative-resistance characteristic, e.g., a Ballast condenser are connected to the secondary side. Conventionally, even upon lighting-on a plurality of discharge lamps, the Ballast condensers are connected to the individual discharge lamps, thereby realizing a multiple-light discharge lamp lighting device (refer to, e.g., Patent Document 1).
Further, upon lighting-on a plurality of discharge lamps, tube current of the individual discharge lamps needs to be equalized so as to make the luminance of the discharge lamps uniform. In the discharge lamp lighting device having a plurality of discharge lamps to which the Ballast condensers are connected, variation in characteristics of the Ballast condensers can cause variation in tube current. Therefore, such one circuit structure is proposed that the tube current of the discharge lamps is equalized by arranging a balance coil on the secondary side of the inverter transformer (refer to, e.g., Patent Document 2). Further, such another circuit structure is proposed that a constant current source with a low voltage is arranged to the primary side of the inverter transformer and the Ballast condenser is not required by supplying current from the constant current source with the low voltage (refer to, e.g., Patent Document 3), and the use of a multiple-light discharge lamp lighting device with the other circuit structure can advantageously equalize the tube current.                Patent Document 1: Japanese Unexamined Patent Application Publication No. 2002-175891        Patent Document 2: Japanese Unexamined Patent Application Publication No. 7-45393        Patent Document 3: Specification of Japanese Patent No. 3256992        